A 3rd generation partnership project long term evolution (3GPP LTE, hereinafter referred to as “LTE”) communication system is briefly described as an example of a wireless communication system to which the present invention is applicable.
FIG. 1 is a diagram schematically illustrating an evolved universal mobile telecommunications system (E-UMTS) network structure as an example of a wireless communication system. E-UMTS is the next stage in the evolution of UMTS and is currently undergoing standardization in the 3GPP. In general, E-UMTS may be referred to as an LTE system. Release 7 and Release 8 of “3rd Generation Partnership Project; Technical Specification Group Radio Access Network” may be referred to for details of technical specifications of the UMTS and the E-UMTS.
Referring to FIG. 1, the E-UMTS includes a terminal (for example, user equipment (UE)), a base station (for example, an eNode B (eNB)), and an access gateway (AG) positioned at the end of a network (for example, an evolved UMTS terrestrial radio access network (E-UTRAN)) and connected to an external network. The base station may simultaneously transmit multiple data streams for a broadcast service, a multicast service, and/or a unicast service.
A base station includes one or more cells. A cell is set to one of bandwidths such as 1.44, 3, 5, 10, 15, and 20 MHz to provide a downstream or upstream transmission service to several terminals. Different cells may be set to provide different bandwidths. The base station controls data transmission and reception for a plurality of terminals. The base station transmits downlink scheduling information for downlink data to inform a terminal of information about a time/frequency domain in which the data is to be transmitted, decoding, data size, a hybrid automatic repeat and request (HARQ), etc. In addition, the base station transmits uplink scheduling information for uplink data to a terminal to inform the terminal of information about a time/frequency domain available to the terminal, decoding, data size, a HARQ, etc. An interface may be used between base stations to transmit user traffic or control traffic. A core network (CN) may include the AG, a network node for registering a terminal user, etc. The AG manages terminal mobility in a unit of a tracking area (TA) including a plurality of cells.
Even though the wireless communication system has been developed into LTE based on wideband code division multiple access (WCDMA), demands and expectations of users and service providers are continuously increasing. Moreover, since other radio access technologies are continuously being developed, new technological evolution is required to remain competitive in the future. There is a desire for reduction in price per bit, increase in service availability, flexible use of a frequency band, simple structure, open interface, appropriate power consumption of a terminal, etc.